Explosively actuated anchor for mine roof bolts



Nov. 6, 1951 R. TEMPLE 0 EXPLOSIVELY ACTUATED ANCHOR FOR MI-NE ROOF BOLTS Filed Sept. 20, 1950 v INVENTOR.

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Patented Nov. 6, 1 951 EXPLOSIVELY ACTUATED ANCHOR FOR MINE ROOF BOLTS Robert Temple, Swissvale, Pa., asslgnor to Temple Velocity Equipment, Inc., Wilmington, Del., a corporation of Delaware Application September 20, 1950, Serial No. 185,707

7 Claims. (Cl. 85--2.4)

This invention relates to the bolting of mine roofs to support them, and more particularly to.

means for anchoring the upper ends of the bolts in the bolt holes.

Up until recently, it was the universal practice to support mine roofs by means of timbers. This required horizontal beams and posts for supporting them. The installation of such timbering is expensive and the posts often take up muchneeded space in the mine passages and rooms. In an eflfort to overcome the disadvantages of timbering, the practice is developing in many mines of supporting the roofs by means of bolts which extend up into holes drilled up into the roofs into the overlying rock. The upper ends of these bolts must be anchored in the rock so that the' heads at their lower ends can tightly engage the roof around the lower ends of the holes to support it. The biggest problem in installing such bolts is to anchor their upper ends in the bolt holes quickly and effectively. Various ways of doing this have been tried, but heretofore none of them has been very satisfactory.

It is among the objects of this invention to provide a. device for anchoring the upper end of a mine roof bolt in surrounding rock which is easy to use, which anchors the bolt very quickly andsecurely, and which is dependable in operation.

In accordance with this invention, an expander is fastened to the upper end of a mine roof bolt which then is inserted in a hole drilled up into a mine roof. The expander has a downwardly tapered lower portion, and an upper portion provided with a downwardly extending bore. The bore contains a charge of explosive powder. The upper part of the expander is encircled by an expansion member which extends downward around its tapered portion. The inside of the lower end of the expansion member is smaller than the upper part of the tapered portion, so that when the charge of powder is detonated and the expansion member is driven upward by the force of the explosion, the lower end of that member will be expanded as it is drawn upward against the tapered portion of the expander. Preferably, the charge is detonated electrically through wires extending from it down and out of the bolt hole.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which Fig. l is a side view of a bolt and a central vertical section of an unexpanded anchor fastened thereto and inserted in a hole drilled upward from the roof of a mine passage; Fig. 2 is a side view of the anchor; and Fig. 3 is a vertical section of the anchor, but showing the relative positions of the parts of the anchor after it has been expanded into the surrounding rock.

Referring to Figs. 1 and 2 of the drawings, a hole I is drilled up into the roof of a mine for several feet. The hole extends up through the shale which is to be supported, and into overlying sandstone when that is present. A headless bolt 2, threaded at both ends, then is inserted in the hole and its upper end is anchored therein so that the bolt can not be pulled down out of the hole. For anchoring the upper end of the bolt in the surrounding rock 3, an explosive-actuated anchoring device is fastened to its upper end.

'In accordance with this invention, the anchor is formed from two principal parts; an outer expansion member 5 and an inner expander 6 for expanding that member. The expander is circular and has a threaded axial opening I in its lower end to permit it to be screwed onto the upper end of the bolt. A portion of the expander encircling this bore is tapered downward to provide a wedge 8. The upper portion of the expander is provided with an axial bore 9 that is filled with explosive powder II. The powder can be detonated by an electric primer l2 disposed in the lower end of the bore and connected to a suitable source of electric current (not shown), by means ofv wires l3 that extend out through the side of the expander and down out of the bolt hole.

The upper portion of the expander isenclosed by the upper portion of the expansion member. Preferably, the upper portion of the expander is reduced in diameter, and for convenience of manufacture the expansion member is formed in two parts. The upper part is in the form of a hollow piston or an inverted cup I5, into which the reduced upper end of the expander extends. The side walls of these two members engage each other tightly in order to hold them together and also to seal the powder against moisture. The lower part of the cup is reduced in diameter and provided with external threads I6, onto which the upper end of an expansion sleeve I1 is screwed. This sleeve extends down past the expander and along the bolt for a short distance. The central part of the inside of the sleeve converges downward along the wedge in sliding engagement with it, while the lower part may be cylindrical and engage the bolt. The outside of the lower portion of the sleeve may be provided with teeth l8 for cutting into the surrounding rock. The sleeve below the cup preferably is provided with a plurality of circumferentiallvsegments that permit the sleeve to be readib expanded. Before expansion, the maximum diameter of the sleeve is no greater than the maximum diameter oi the cup, and the sire of the cup is such that the anchor can be pushed up into the bolt whole without binding and yet with little clearaneebetweenitandthewalloi'thehoie.

Before the anchor is pushed up into the hole by means or the bolt, a heavy plate 2! is slipped up onto the lower end 01' the bolt and held in place by a nut 22. This plate serves as an enlarged head for the'bolt. The bolt then is inserted in the hole until the plateis close to, or practically engages, the root of the mine with wires il extending out from the'edge oi the plate.

The lower end the bolt, may be supported in this position by a Jack or post 23. This-post not only supports the bolt temporarily, but it prevents any recoil from the explosion of powder in the anchor from moving the bolt downward.

With the anchor and bolt in position in the hole, as just described, electric current is supplied through wires it to the electric primer i2 to detonate the charge of powder in expander t. The upper end of bore a may be flared so that sub:

stantially the full area of the overlying surface of cup II will be exposed to the force ot'the explosion from the start. The force of the 'explosion drives the overlying cup or expansion member 8 upward in the bolt hole and thereby pulls the tapered segments 0! expansion sleeve ll upward on the wedge I. as shown in Fig. 3. The

' we'dge forces the sleeve segments outward into the surrounding rock as they move upward, so that the expansion member can not be moved downward. It therefore serves as a strong support for the bolt that is suspended from the expander. Following this operation, which takes only a moment, the nut 22 at the lower end of the bolt is screwed upward to force plate 2| uptightly against the mine root-to prevent the root from telling. Later, if desired, the bolt can be salvaged by unscrewing it from expander 6.

It will be seen that the anchor described here-/ stood that, within the scope oi the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. An explosive-actuated mine root bolt anchor, comprising an expander adapted to be tastened to the upper end or a bolt inserted in a hole drille'd up into a mine ml, the expander having a downwardly tapered lower portion and having an upper portion provided with a downwardly extending bore, a charge or explosive powder in -he bore, an expansion member enclosing the upper part 01' the expander and ex.- tending downwardaround said tapered portion, the inside of the lower end or said member being smaller than the upper part 01' said tapered portion, and means i'ordetonating said charge to drive said member upward, whereby the lower end of the expansion member will be expanded by the tapered portion oi the expander.

spaced vertical slots I! which separate it into 2. An explosive-actuated mine root bolt anchor, comprising an expander adapted to be ias- I toned to the upper end'oi a bolt inserted in a v hole drilled up into a mine root, the expander having a downwardly tapered lower portion and having an upper portion provided with a down.-

extending bore. a charge of explosive powwardly I der in the bore, an expansion member enclosing the upper part oi the expander and extending downward around said tapered portion, the inside of the lower end 01' said member bein smaller than the upper part of saidtapered portion, and an electric primer in said bore for deta holedrilled up into a mine root, theexpander having a downwardly tapered lower portidrand having an upper portion proyideduwith a downwardly extending bore; a charge of explosive-powder in the bore, an expansion member enclosing the upper part of the expander and extending downward around ,said tapered portion, the inside of the lower end 01' said member being smallerthan the upper part 01 said tapered portion, the lower end portion of said member being provided with a plurality of upwardly extending slots separating it into segmentaand means for,

detonating said charge to drive said member upward, whereby said segments will be forced outward by the tapered portion of the expander. 4. An explosive-actuated mine root bolt anchoricomprising an expander adapted to be tastened to the upper end of a bolt inserted in a --hole drilled up into a mine roof, the expander having a downwardly tapered lower portion and having an upper portion providedwith a downwardly extendingxbore, a charge or explosive powder in the bore, an expansion member enclosing the upper part of the expander and extending downward around said tapered portion, said member 'havinga downwardly converging inner surface engaging the tapered portion oi the expander, and means for detonating said charge to drive said memberupward, whereby the portion of the expansion member engaging the tapered portion of the expander will be expanded by it.

5. An explosive-actuated mine rooi' bolt anchor, comprising an expanderadapted to be rastened tothe upper end of a bolt inserted in a hole drilled up into a mine roof, the expander having a downwardly tapered lower portion and having an upper portion provided with a downwardly extending bore, a charge of explosive powder in the bore, a cup ntting tightly over the upper part of the expander, an expansion sleeve en- I circling the expander and connected to the cup and extending downward around said tapered portion, the inside 01' the lower end oi the sleeve being smaller than the upper part 01' said tapered portion, and means for detonating said charge to drive said cup and sleeve upward, whereby the lower end of the sleeve will be expanded by the tapered portion of the expander.

8. An explosive-actuated mine root bolt anchor, comprising an expander adapted to be tastened to the upper end of a bolt inserted in a hole drilled up into a mine root. the expander having a downwardly tapered lower portion and 15 mm: an pp r portion provided with a downwardly extending bore, a charge of explosive powder in the bore, a cup fitting over the upper part 01 the expander, an expansion sleeve screwed onto the lower end of the cup and extending downward around said tapered portion, the sleeve having a downwardly converging inner surface engaging the tapered portion of the expander, the sleeve also being provided with a plurality of upwardly extending slots separating it into segments, and means for detonating said charge to drive the cup and sleeve upward, whereby said segments will be forced outward by the tapered portion of the expander.

7. An explosive-actuated mine roof bolt anchor comprising an expander provided in its lower end with a threaded opening for receiving the threaded upper end of a bolt inserted in a hole drilled up into a mine roof, the portion of the expander around said opening being tapered downwardly, the upper portion of the expander being provided with a downwardly extending bore, a charge oi explosive powder in the bore, an expansion member enclosing the upper part 01. the expander and extending downward past said tapered portion, the inside of the lower end of said member being smaller than said tapered portion, and means for detonating said charge to drive said member upward, whereby the lower end of the expansion member will be expanded by the tapered portion of the expander.

ROBERT TEMPLE.

No references cited 

